Pulling fuel and metals from seawater, still at lab scale

PNNL researchers say 0.1% of the world's seawater holds enough critical elements to meet energy needs for 50,000 years — if extraction can scale.

Researchers at the Department of Energy's Pacific Northwest National Laboratory are developing three processes to extract minerals from seawater. Their striking framing: just 0.1% of the world's seawater contains enough critical elements to power humanity for 50,000 years. So far the team has recovered magnesium, lithium, nickel, platinum-group metals, and rare earths from seawater or seawater-derived chemicals, and eight years ago extracted 5 grams of uranium in earlier work.

Magnesium is where the numbers are strongest. A 600,000-gallon volume of seawater holds just 0.42 kg of lithium but 2,980 kg of magnesium. PNNL's patented co-flow reactor runs seawater alongside sodium hydroxide to make high-purity magnesium hydroxide, cutting at least four steps from the traditional Dow process. Modeled at California's Carlsbad desalination plant — which handles 108 million gallons a day — the concept could yield 524,000 kg of magnesium hydroxide daily at full recovery, more than triple current US usage. The US mined magnesium from seawater for about 50 years before switching to imports in the 1990s.

If it scales, seawater becomes a domestic, effectively inexhaustible feedstock for the metals that batteries, grids, and clean energy depend on — loosening a major supply bottleneck.

The caveats are heavy. Most critical elements sit at concentrations too dilute to extract economically, and the central challenge is making the technology economically feasible at scale. The Carlsbad figures assume 100 percent recovery in a model, not real operation. Everything here is described as in development.

Source: New Atlas